Effect of Verapamil on the Normal Action Potential and on a Calcium Dependent Slow Response of Canine Cardiac Purkinje Fibers
Effect of Verapamil on the Normal Action Potential and on a Calcium Dependent Slow Response of Canine Cardiac Purkinje Fibers
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维拉帕米对犬心脏浦肯野纤维正常动作电位和钙依赖性慢反应的影响
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发表时间：
1974
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通讯作者：
A. L. Wit
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作者：
P. Cranefield;R. Aronson;A. L. Wit
研究了维拉帕米对犬心脏浦肯野纤维记录的正常钠 (Na) 依赖性和慢钙 (Ca) 依赖性动作电位的影响。在暴露于溶液中的纤维中获得依赖于 Ca 的缓慢响应，其中所有 NaCl 均被四乙基氯化铵取代，并且其中 Ca 的范围为 4 mM 至 16.2 mM。维拉帕米（0.25-2毫克/升）对正常动作电位的上冲影响很小或没有影响，但这种浓度的维拉帕米会抑制节律活动并降低纤维的兴奋性，从而表现出钙依赖的缓慢反应。由长去极化脉冲引起的自发活动和节律活动被抑制。维拉帕米降低了振幅和上冲速度，并将显示钙依赖性缓慢反应的纤维中的阈电位移向零。维拉帕米的有效性随 Ca 水平的不同而变化。 0.25 mg/升维拉帕米在抑制暴露于 4 mM Ca 的纤维中的活性与 2 mg/升维拉帕米在暴露于 16.2 mM Ca 的纤维中一样有效。尽管维拉帕米没有改变正常Na依赖性动作电位的上升，但它确实降低了平台并延长了暴露于正常Tyrode溶液的纤维的动作电位。
The effect of verapamil on normal sodium (Na)-dependent and slow calcium (Ca)-dependent action potentials recorded from canine cardiac Purkinje fibers was studied. The Ca-dependent slow response was obtained in fibers exposed to solutions in which all NaCl was replaced by tetraethylammonium chloride and in which Ca ranged from 4 mM to 16.2 mM. Verapamil (0.25–2 mg/liter) had little or no effect on the upstroke of the normal action potential, but such concentrations of verapamil suppressed rhythmic activity and depressed excitability in fibers that showed Ca-dependent slow responses. Spontaneous activity and rhythmic activity evoked by long depolarizing pulses were depressed. Verapamil decreased the amplitude and the upstroke velocity and shifted the threshold potential toward zero in fibers that showed Ca-dependent slow responses. The effectiveness of verapamil varied with the level of Ca; 0.25 mg/liter of verapamil was as effective in suppressing activity in fibers exposed to 4 mM Ca as was 2 mg/liter of verapamil in fibers exposed to 16.2 mM Ca. Although verapamil did not alter the upstroke of the normal Na-dependent action potential, it did depress the plateau and prolong the action potential of fibers exposed to normal Tyrode's solution.